Hardening accelerators are used in mineral binders for hardening binder compositions after mixing with water. Hardening accelerators can be used, for example, in order to cast concrete at low temperatures or to increase the early strength of mortar or concrete compositions.
In this context, various substances can be used which accelerate the hardening of mineral binders, for example, cementitious binders. Such substances include, for example, hardening accelerators based on amino alcohols, halides, pseudohalides, nitrites, nitrates, aluminum salts, alkali hydroxides, alkaline earth hydroxides, glycols, glycerol, or α-hydroxycarboxylic acids.
WO 2003/000617 A1 (Sika AG) describes, for example, a hardening accelerator based on an alkanolamine, an inorganic nitrate, a carboxylic acid, and a polyol. Examples of amino alcohols are monoethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, and triisopropanolamine.
However, the known hardening accelerators have various disadvantages. Thus, in the case of halides, pseudohalides, nitrites and nitrates in concrete, there is a risk of stress crack corrosion of pre-stressing steels. Alkali hydroxides, aluminum salts, glycols and glycerols often have an undesired stiffening behavior, and α-hydroxycarboxylic acids are dosage sensitive. In this regard, known amino alcohols can be more advantageous; however, they are not entirely satisfactory with regard to hardening acceleration.
Therefore, there continues to be a demand for improved hardening accelerators for mineral binders, which do not have the above-mentioned disadvantages.